One of the present inventors proposed a gripper having a very simple mechanism in the official gazette of International Patent Publication No. WO99/30877. This gripper is characterized in that a small quantity of translational movement is transformed into a quantity of bending displacement being enlarged tenfold or more at a tip of each finger of the gripper by applying a buckling phenomenon of a long column to the finger without using a specific displacement enlarging mechanism.
With this gripper, it becomes possible to softly hold a very small part. Further, since the size of this gripper is small and the weight is light, this gripper is suitably used for a robot hand.
However, the present inventor made investigations in earnest and found the following. In a case where the gripper is applied to the use for holding an object by conducting a predetermined opening and closing motion, a quantity of opening and closing a gripping member for holding the object must be set at an appropriate value. Therefore, it is necessary to adjust the rotary angles of a motor in the forward and backward rotating directions so that a quantity of translational displacement of reciprocation at the other end of the gripping member becomes a predetermined value. This operation is complicated. In view of this, the inventor filed an international application of electric tweezers (International Application No. PCT/JP/11839).